JULY/AUGUST 2023 AFTERMARKET 25 A new sensor had been previously fitted, so came my Pico to check CAN high/low, with confirmed distortion and a strange voltage pull up to around the 8-volt range. Checking the wiring codes to the sensor, all colours matched factory spec, which means they are incorrect. Why? The replacement OEM Bosch sensor had also been modified, which required a wiring modification. Please refer to Fig.4. C1 WHITE/BLUE +12v C2 VIOLET CAN H C3 VIOLET /WHITE CAN L C4 BLACK GROUND C5 X Once corrected CAN was restored, all DTCs cleared and all adaptive procedures were carried out. Please refer to Fig.5, showing the Pico CAN waveform. Engineering tasks Finally, some engineering tasks. Two consecutive days saw broken injector bolts come into the workshop, I suspect due to using power tools and not applying a more controlled smooth torque via a hand ratchet. The first had broken the bolt and striped the thread in the process. The break was flush with the top face so cantering a drill was not a problem. The bolt core came out relatively easily with an easy out. The next task was fitting an 8mm helicoil, in fact I fitted two due to the length of thread on the clamp bolt .Please refer to Fig.6, showing the helicoil kit. The second breakage was not so simple; The clamp bolt had sheared 20mm down the bore. Centring the drill was going to be very risky. Not a problem with the head off using a pedestal drill. By a lucky twist of fate there was a 9mm counter bore before the 8x1.25 mm thread. I elected to manufacture a drill guide tool, 15mm into and 15mm above the hole. A 6mm centre allowed me to confidently centre drill the bolt in situ. Please refer to Fig.7, showing the special tool and drill. This is where engineering infrastructure and experience comes in. The broken bolt was so hard none of the available drills would cut. I have previously explained that my main toolbox is at home, and for good reason, so I had to select a cobalt drill from my personal drill set. There are several ways to identify a cobalt drill. For one thing, the shank will carry the abbreviation CO. Alternatively the cutting head may, but not always, have multiple cutting angles. Normally 5%-8% cobalt. Please refer to Fig. 8. Do not use a cutting lubricant with a relatively high cutting speed. Knife through butter came to mind as the 6mm centre drill went down the bolt perfectly. The tapping drill for 8mm is 6.8mm so a conservative 7mm drill would help clear the old thread swarf from the bore. Using first, second, and plug taps restored the original thread, due to the depth of the thread. It was necessary to raise the taps to clear the flute of swarf and residual debris from the thread bore. This type of repair is never a race against time. A new head casting was £2,500 plus labour. I don’t know what the customer was charged I would value the task at £400- £500, half a day’s labour. Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 www.aftermarketonline.net
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